The changes from d789bca that were made as part of SERVER-18498 made mixed version replication tests use protocol version 0. At the time, this was necessary because the "last-stable" version referred to 3.0 and protocol version 1 wasn't supported; however, it doesn't look like we updated any of the modified multiversion tests to use protocol version 1 since we branched.

• jstests/multiVersion/2_test_launching_cluster.js
• jstests/multiVersion/downgrade_replset.js
• jstests/multiVersion/initialsync.js
• jstests/multiVersion/minor_version_downgrade_replset.js
• jstests/multiVersion/mixed_storage_version_replication.js
• jstests/multiVersion/wt_index_option_defaults_replset.js